Using UPS's for off-grid use.

[labeeman]

Set up that I have is 12, 180-watt panels hooked up to a Growatt solar charge controller keeping charged up a 100 amp hour 48 VDC battery has been up for 22 days. I have a 3KVA UPS hooked up powering some lights and a computer it discharges to 50% every night and is charged up the next day by noon unless it is cloudy. 3 days ago it was cloudy for 2 days and the battery was down to 10% I hooked up the UPS to the grid and turned on the breaker it complained and the UPS did to then everything went back to normal. I have now figured out what happened after 20 or so days the frequency of the UPS had drifted to where the Grid and the UPS were at odds and a large current flowed when I threw the breaker. The lesson is to use a separate battery charger and not the UPS charger to keep the battery charged up.

 

[sunshine_eggo]

Yeah. UPS charge rate is absurdly low, and they typically only charge to 13.8V and hold there. It can easily take 24 hours to get a battery fully charged on a UPS.

 

[labeeman]

This UPS will charge up to 57.5V but only at 3 amps. At that rate, it would take 33 hours for one battery and I plan to have 11 of them.

 

[crossy]

In addition to the pitiful on-grid charge rate UPS's aren't really intended for continuous operation on battery.

The internals are designed to run for the autonomy time of the internal batteries without cooking, but running them longer (bigger batteries) at anywhere near full output will likely lead to overheating and failure unless you add cooling fans and possibly bigger heatsinks.

If you have one "in stock" then by all means use it, but the real solution is to source an inverter intended to run 24/7/365.

EDIT If you have an (expensive) dual-conversion or on-line UPS rather than the common line-interactive UPS it WILL happily run forever at full power, but the charger will also be able to keep up with the output power (for the OP's 3kVA unit that would be charging at 60A @ 48V).

What are the different types of UPS?

UPS devices deliver critical equipment protection. Uninterruptible Power Supplies offer a full range of power management solutions.

www.comms-express.com

 

[labeeman]

The ones I have are server room UPS they only draw one amp at 57V with no load. I have 3 of them at 2700 watts each.

 

[crossy]

The ones I have are server room UPS they only draw one amp at 57V with no load. I have 3 of them at 2700 watts each.

There's a strong possibility that they are of the on-line type and would be designed for high reliability too. What manufacturer / type are they?

 

[labeeman]

They are the common line-interactive UPS

APC SmartUPS 3000VA 2700W RM 2U SUA3000RM2U​

 

[crossy]

I'd just watch for overheating issues then, if they're not brewing up then all are happy.

My initial comments were aimed at those intending using the lower-cost "workstation" UPS's your beasts being intended for server use would be designed to a higher standard. Many of the ones we use also have the facility to add external battery packs for effectively unlimited run time so of course the comments wouldn't apply.

 

[labeeman]

I load tested one of them to see if my battery was up to snuff 4 hours at 1200 watts.

 

[crossy]

Sounds like you're good to go

 

[labeeman]

Yep they are beasts at 60# each they are the low-frequency type with most of the weight in the transformer.